This invention deals with the subject of providing handrails for curved staircases. Curved staircases are important architecturally, both as aesthetic variations from ordinary staircases and to provide staircases to accommodate to difficult architectural situations. Typically, a spiral staircase is effective for small floor areas or where staircases are added by remodeling.
Modern architecture employs free-form staircases which, with modern developments, are easy to make and attractive. For example, U.S. Pat. No. 3,474,882 describes prefabricated modular elements capable of being assembled into staircases of substantially any form or shape. Spiral and modern free-form staircases have many advantages. They are prefabricated and therefore are relatively inexpensive. They are modular and the modules can be assembled into staircases of substantially any shape and size to fit any architectural situation. The modules may be shipped flat and broken down and assembled at the site of use rather than built there. This feature greatly reduces the cost of such a staircase. Modern modular staircases are capable of being formed in helical segments from flat parts. Curved segments, helical segments, and straight segments can be intermixed to form substantially any size or shape.
Although modern, modular curved staircases are inexpensive to make, to ship, and to assemble, the handrails for such staircases are difficult to produce, ship and assemble. Handrails desirably are continuous and such handrails must be shipped in one piece. It is axiomatic that as the staircase becomes more complicated in its curves and forms, the handrail also becomes more complicated. In many cases, handrails are even more complicated than the staircase they were made for because the handrail on the inside of a curve in a staircase must have a different length and pitch than the handrail on the outside of the curved staircase. Additionally, long helical handrails must not only accommodate to the length and pitch of the particular part of the staircase they are designed to adapt to but they themselves must be formed as helixes. For example, if a helical handrail for a spiral staircase would have a line drawn along its upper crest for its entire length and if that handrail were then disassembled from the staircase and straightened, that straight line would become a helix spiraling around the surface of the handrail.
As a result of the foregoing problems, beautiful, imaginative, unique, useful curved staircases can now be readily made inexpensively, but the handrail to fit such a staircase is expensive in design and execution and it is difficult to install.